This invention relates to novel aromatic copolyetherimides and a method for their preparation by a phase transfer catalyzed reaction.
Various types of aromatic polyethers, particularly polyethersulfones and polyetherketones, have become important as engineering resins by reason of their excellent properties. These polymers are typically prepared by the reaction of salts of dihydroxyaromatic compounds, such as bisphenol A disodium salt, with dihaloaromatic molecules such as bis(4-fluorophenyl) sulfone, bis(4-chlorophenyl) sulfone and the analogous ketones.
These reactions previously required the use of dipolar aprotic solvents, which were necessary to solubilize one or both reactants. Such solvents are expensive, difficult to purify and difficult to keep dry, since they readily dissolve water. Moreover, the polymers prepared by the use of such solvents are frequently colored by reason of the occurrence of side reactions leading to colored by-products.
Another class of polymers capable of preparation by a similar method is the polyetherimides. U.S. Pat. Nos. 3,787,364, 3,838,097 and 3,847,869 describe their preparation by the reaction of salts such as bisphenol A disodium salt with halo- or nitro-substituted bis(phthalimido) derivatives of aromatic diamines. These methods of preparation also require dipolar aprotic solvents. In addition, they frequently do not afford products of high molecular weight or in high yield. As a result, polyetherimides are normally produced on a commercial scale by the reaction of diamines with bis(ether anhydrides). The latter reagents are generally themselves produced by a complex multi-step synthetic method often employing nitro-substituted phthalimides, which lead to the formation of by-products hazardous to the environment in varying degrees.
There has been considerable attention directed in recent years to methods for conducting organic reactions in heterogeneous systems, employing a phase transfer catalyst which facilitates migration of a reactant into a phase from which it is normally absent. Thus, for example, it is known that bis(ether anhydrides) may be prepared by the reaction of a bisphenol disodium salt with a nitro- or halo-substituted phthalimide in a methylene chloride-water mixture, employing a phase transfer catalyst to promote migration of the otherwise methylene chloride-insoluble bisphenol salt into the organic layer for reaction with the substituted phthalimide.
U.S. Pat. No. 5,229,482 discloses a phase transfer catalyzed reaction for the preparation of polyethers. Said reaction occurs between at least one alkali metal salt of a dihydroxy-substituted aromatic hydrocarbon and at least one substituted aromatic compound which may be, for example, a bis(substituted phthalimide), a bis(halophenyl) sulfone or a bis(halophenyl) ketone as indicated hereinabove, in the presence of a catalytically active amount of a phase transfer catalyst which is substantially stable at the temperatures employed. There is no disclosure, however, of copolyetherimides containing other types of structural units or a method for their preparation.